404SEF allows Search Engine Friendly URLS without the need for mod_rewrite, returns proper 404 status code for missing content and provides logging of 404 errors.

A6Mambocredits will display credits for each installed Mambo component on one central page.

Acctexp let's you manage the expiration of user accounts.

Akobook342 - A complete guestbook solution with editor support, autopublish, email notification, multiple fields, pagination, smilies, bbcode, SEF support, language file support and many more.

Akocomment20 - Let's your users comment on your content items

DataDisplay - A simple module that will extract and display data from any joomla table.

Yahoo YPN Plugin - This modification of existing Adsense Plugin (Mambot) is extremely helpful to place ads directly in the content item

StopPress Banner Module will pop up a configurable DHTML Box containing banner from Joomla system when people visit your web

Picasa Referral Module - Picasa is a photo organizer software released by Google.

Onet Kontekst Module - Onet Kontekst ads (Polish, similar to Google AdSense) module for Joomla.